Key result
Verapamil and nitrendipine exert greater negative inotropy in immature versus adult myocardium.
Why the study?
The mechanisms regulating calcium influx across the sarcolemma and their postnatal maturation effects on myocardial contractile responses to calcium antagonists were unclear.
Population
Right ventricular papillary muscles isolated from immature (14-21 days) and adult rabbits
Comparison
Verapamil and nitrendipine effects vs absence of calcium antagonists; immature vs adult myocardium
Design
Preclinical experimental study
Authors
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Requires caution extrapolating calcium antagonist effects from adult to pediatric models; leaves open postnatal maturation of calcium influx in humans.
p-value: p=<0.05
Immature rabbit myocardium shows greater sensitivity to the negative inotropic effects of calcium antagonists compared to adult myocardium, suggesting postnatal maturation of calcium influx mechanisms.
Artman et al. (1985) studied this question. Verapamil and nitrendipine vs. Adult rabbit myocardium was evaluated on Concentration reducing basal developed tension by 50% (p=<0.05). Immature rabbit myocardium exhibited greater sensitivity to the negative inotropic effects of verapamil and nitrendipine compared to adult myocardium (p<0.05 for both).
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